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Famous Scientists, Doctors and Inventors / Catalogue shopping - who came up with that?

« on: 02/11/2007 13:10:25 »

Found this :  (in http://inventors.about.com/library/inventors/blshopping.htm)

Mail Order Catalog
Aaron Montgomery Ward sent out his first mail order catalog in 1872 - for his Montgomery Ward mail order business located at Clark and Kinzie Streets in Chicago. The first catalog consisted of a single sheet of paper with a price list, 8 by 12 inches, showing the merchandise for sale with ordering instructions.

"Ward's gradually expanded the catalog. They became bigger, more heavily illustrated, chock full of goods-- often referred to as "dream books" by rural families."
Aaron Montgomery Ward was born on Feb. 17, 1844 and died on Dec. 7, 1913. He first worked for Marshall Field, a department store, as both a store clerk and a traveling salesman. As a traveling salesman, he realized that his rural customers could be better served by mail-order, a revolutionary idea. He started his business with only $2,400 in capital. Montgomery Ward was a mail-order only business until 1926, when the first Montgomery Ward retail store opened in Plymouth, Indiana.
1872 Montgomery Ward-First Mail-Order House
Catalog Image :  http://www.chipublib.org/images/timeline/wardwatchesm.JPG

In Germany, the first catalogue appears to be dated 1888, In France, Begium or the Netherlands, things start even later.
But trading by lists of goods from which only small samples were available was current on the famous fairs in the late Middle Ages (say 13th and 14th century) because the cities where the fairs took place charged way too much for storage.

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General Science / Re: Why does a gas flame not track back inside the supply pipe?

« on: 31/10/2007 18:49:30 »

Bunsens are different in the sense that you can regulate the air flow with them, and that they do not have this little holes where the flame is formed.  (That's why you can have this blow back in a Bunsen.)
But take a standard gas stove.  The flame is formed above a circular tube, with holes in the top side.  This tube is linked to the gas supply by a straight section of tube, that ends a couple of mm from the gas tube.  There you have the jet or nozzle, through which the gas flows.  As there is some free space between that jet and the tubing, air flows in with the gas (venturi effect).
If you change jets, e.g. because you switch from butane to natural gas, you may have to change the distance between the end of the pipe and the jet.  Too short means not enough air and a yellow flame; if too long you have irregular burning because the flame tends to be blown away from that ring. You don't need to change jets when you switch from butane to propane (or vice versa); and if changing is needed, have it done by a qualified installer.  That will save you a lot of trouble and time.

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The Environment / manufacture of ethanol

« on: 31/10/2007 09:09:33 »

The ethanol is produced from the corn kernels, not even from the complete ear.  The stems are used cattle feed mainly, and the "woody" part of the ear is often used as fuel.  (In fact, I know of no other application yet, although fibreboard production may be a possibility). 
The advantage of cereals (corn, wheat, rice or whatever) is that they can be dried at or near the place where they are grown, and as dried product can be stored over many years.  This means that you have the possibility of a constant rate of production of ethanol over the year, while sugar beets or sugar cane are typically "campaign" products.  Of course, you could use the campaign to produce sugar, and use the sugar to produce ethanol during the rest of the year.

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The Environment / can you measure the thickness / width of a rainbow?

« on: 31/10/2007 08:45:06 »

and, are all the sections of different colours of equal width in a rainbow?

Actually, there are no "sections" but a gradual passage from red to violet.  It's just that we have no proper name for every shade that makes us divide the rainbow in sections.

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General Science / Re: Why does a gas flame not track back inside the supply pipe?

« on: 30/10/2007 17:22:36 »

Alberto, I'm not trying to start a dynasty, so it's eric L (for the first character of my surname) rather than eric I.  But the mistake often does make me smile.

And as long as the gas does not build up around the leak, but disperses quickly, this electric welding may work - in the hands or real professionals.

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Chemistry / Working out the concentration of a stock solution..

« on: 30/10/2007 16:12:12 »

[Edit: eric l has actually used the molar mass for the dihydrate straight from Wikipedia, so his working should actually be ok. For any kind of test however, you'd be expected to calculate the molar masses from scratch, and you'd be wise to explicitly account for the WoC.

I took it for granted that with an online test, you had access to all sources on the internet, including Wikipêdia - just like we in our times had access to all catalogues of chemical compounds and even to the labels on the bottles with an "open book" test.
Of course, it does not harm to check the Wikipedia information with other sources (on the web or elsewhere).  Personally, I would go for the Material Safety Data Sheets - if available.

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General Science / Re: Why does a gas flame not track back inside the supply pipe?

« on: 30/10/2007 15:07:24 »

There are a number of reasons, and this list will probably quite incomplete.

• a fuel can only burn when it is mixed with air in a ratio between definte values (depending on the fuel), a mixture that is either too rich or to lean (in fuel) does not burn
  
• the gas comes from the pipe through a nozzle, only after which it is mixed with air; the gas in the pipe does not contain enough oxygen to burn
• there is also the speed of the flame front, if the speed of the mixture of gas and air is higher than this speed of the flamefront, the flame can not travel back to the nozzle
• the flame is formed on the gas ring, a perforated tube.  The perforations make sure that the speed of the mixture remains high and the metal acts as a kind of heat sink so that the mixture inside remains cooler than the "flash point" (http://en.wikipedia.org/wiki/Flash_point)
  

See also :
- http://en.wikipedia.org/wiki/Bunsen_burner
- http://en.wikipedia.org/wiki/Gas_burner
- http://home.howstuffworks.com/how-to-repair-an-oven.htm

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Chemistry / Working out the concentration of a stock solution..

« on: 30/10/2007 08:35:16 »

What precision do you want ?  You made the solution by diluting to a volume, and want the concentration by weight.
You could have had that volume in "Mohr litres", which would have excluded doubts, because that obsolete unit was defined as the volume of 1 kg of pure water at the given temperature.  But les us accept the density of water - and of our solution - as 1 g/cm³.
Now we look for the molecular weight of our compound.  Wikipedia (http://en.wikipedia.org/wiki/Calcium_chloride) gives us 147.02.
So the concentration of the solution is (3.668 / 147.02) moles/l.
Each molecule contains 1 atom of Calcium, atomic weight (again according to Wikipedia)
40.08. 
This means we have 40.08*(3.668/147.02) g/l of calcium.  Multiply by 1000 for mg, and take that value in mg/l as equal to ppm.

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Physics, Astronomy & Cosmology / how do hot air balloons come down?

« on: 29/10/2007 09:02:19 »

I see quite a few come over where I live and as they get lower there often seems to be frantic blasting with the burners to keep the rate of descent modest!

I can imagine that !  When driving a car, one gets accustomed to immediate response to trottle, brake or steering wheel.  In a hot air balloon, the response to switching on the gas may take as long as a minute - which means a lot of descent.
With really experieced balloonists, you will observe this frantic blasting of burners only when they notice that the projected landing site they are aiming for is not really suited for some reason.

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General Science / Re: Why would metal, kill yeast in baking situations?

« on: 28/10/2007 08:32:41 »

Well, the initial question read "Why does would metal kill yeast..." so I thaught it might have been a spelling error.

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Chemistry / ¿How does a PHmeter's electrode works?

« on: 27/10/2007 11:31:01 »

Lots of good links to be found by Googling, like these !

• http://www.sensorex.com/support/education/pH_education.html (from about half way the page downwards)
• http://en.wikipedia.org/wiki/PH_glass_electrode
• http://www.eutechinst.com/tips/ph/14.pdf[.li]
  

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General Science / Re: Why would metal, kill yeast in baking situations?

« on: 24/10/2007 17:02:16 »

Oh, Karen, "Why does would metal...", you were not referring to what is known as "Wood's metal", would you ?  It is a kind of solder, and it is unfit for baking conditions.  I don't know about its effect on yeast, but it melts at temperatures like 80°C.  It would melt in the oven.

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General Science / Re: Why would metal, kill yeast in baking situations?

« on: 24/10/2007 10:45:59 »

and who is going to eat all that stuff ?

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Chemistry / Barium oxalate - help appreciated please

« on: 24/10/2007 08:45:37 »

Bariumhydroxide is probably readily available, and most probably as monohydrate (the most stable form).  (You must take that into account for calculating the amounts of each reagent.)

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General Science / Re: Why would metal, kill yeast in baking situations?

« on: 24/10/2007 08:22:09 »

How about copper or aluminium - they are the most likely metals to have been used for mixing bowls in the past?

Again from memory :  copper and aluminium themselves don't harm yeast activity, but some alloys do - e.g. brass will kill off yeast almost instantaneously.  (In one of the cases mentionned above they had used solder that wasmeant for brass for repairing the brewing kettle).

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General Science / Re: Why would metal, kill yeast in baking situations?

« on: 23/10/2007 20:43:47 »

I agree with BC :  the only valid statement would be that SOME metals are harmfull in brewing and baking conditions.
From memory, I can state that calcium (which after all is a metal, too) is actually favourable to the working of yeasts and especially of amylases.  In fact, brewing with soft water is no easy task.
Zinc on the other hand is used to stop amylase activity (in other situations than baking or brewing).
I know of one or two cases were repairs to brewing kettles turned out badly because either the sheet metal or the solder used were not up to specifications (or were incorrectly specified in the first place).

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General Science / What Determines The Size Of drops ?

« on: 22/10/2007 08:43:37 »

I'm affraid most of the guesses are wrong.

• Pasteur pipettes are named after Louis Pasteur (http://en.wikipedia.org/wiki/Louis_Pasteur), who invented them, no doubt about that
• Pasteur's pipettes were glass pipettes with a rubber squeezer, rather than the disposable plastic things known as Pasteur pipettes now; the glass part was sterilizable or disposable
• the squeezer part is not intended to contain liquid, just air.  You press the squeezer, put the tip in the liquid and by releasing the squeezer you have a relative vaccuum sucking up the liquid; you dispense by pushing the squeezer again
• the marks on the stem part are there to indicate the volume dispensed
• when a drop can fall off freely, the size of it is determined by a)the outer diameter of the end of the tip, b) the surface tension of the liquid and c) the density of the liquid 
• Pasteur pipettes are mainly used to dispense in direct contact with some surface (filter paper, Petri plate or other), so drop size does not really matter.  The use as eye droppers is quantitatively less important.

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Physiology & Medicine / At What Age Do We Stop Growing ?

« on: 21/10/2007 09:15:29 »

This may be related only indirectly to the question, but i was told that bone stops growing at an earlier age than cartilage does; in fact some tell me that cartilage never stops growing, which is why elderly people have longer noses and bigger ears.

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General Science / What's this RED liquid in my old Thermometer ?

« on: 20/10/2007 09:58:53 »

The red liquid is alcohol (ethanol) with a colorant.  You'll also find alcohol with a blue colorant.
I thought that mercury was more or less outlawed for thermometers now.  I know that they are no longer used in a lab environment because of the toxicity of mercury vapour (in case of a thermometer breaking - which happens only too often).
Alcohol works better for sub zero temperatures (centigrade); for temperatures above 90°C we used pressurised thermometers (or rather with higher resistance to pressure) or thermometers filled with an other liquid.

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General Science / how could i make home made night vision glasses?

« on: 19/10/2007 16:46:04 »

I remember reading something about an "image intensifier" based un bundling glass fibres and not needing electronic amplifying.  But I never saw one in action, and I don't recall reading about it again - and that must be for something like 10 years.  Maybe it was just a hoax.